The tone generator disclosed in this application represents a further development in the tone generator construction disclosed in application Ser. No. 917,174, filed June 20, 1978, now U.S. Pat. No. 4,160,132 which also is assigned to the assignee of this application. Tone generators of the type involved here are high production items adapted and intended primarily for use in automotive vehicles, a typical application being to produce the sound that serves as a seat belt reminder to the operator. When used for this purpose, tone generators must all produce a uniform and essentially identical tone in order to satisfy customer specifications and they must all be tested for sound prior to delivery. In the predecessor construction referred to above, however, it was not possible to test the tone generator for quality of sound until after final assembly; and, if an adjustment or correction was necessary, it was a relatively difficult and time consuming job to disassemble the generator and make the necessary changes.